1Technical Field
This invention pertains to a method and device for improving the safety of a user of an extension ladder. The method involves installation and use of a device to prevent a fly section of the extension ladder from accidentally descending.
2 Background Art
Extension ladders consist of a base section and one or more fly sections, each fly section extendable from the preceding section. The term "base section" shall be used herein to refer to the lower of two adjacent sections of an extension ladder, from which a fly section is extended upward. Thus, a "base section" may be the section of the ladder onto which the user first climbs, or may be a fly section extending from a previous base section, from which another fly section is extendable.
Most extension ladders rely on rung locks to hold a fly section in place, once it has been extended from a base section Rung locks are typically attached at one end to the interior of the dual rails on the fly section, in a manner which permits an open jaw at the other end of the rung locks to engage a rung on the base section. For ease in extending and contracting the fly section, rung locks are pivotally mounted so that they may be swung away from the rungs of the base section while the fly section is moved up or down.
Failure to properly engage rung locks is a frequent cause of ladder accidents. Falls from ladders account for hundreds of thousands of emergency room admissions each year. "Telescoping" of extension ladders due to false latching or improperly engaged rung locks precipitate many such accidents. If a rung lock is not properly engaged, the fly section of the extension ladder may telescope or descend in a rapid and uncontrolled manner, causing the user to fall. The potential danger is exacerbated by the fact that misaligned rung locks are not always observable from the ground.
In some cases, rung locks may be only partially misaligned, permitting the fly section to be held in place while the user ascends the ladder. However, forces associated with the descent of the user may cause the improperly engaged rung locks to become disengaged, resulting in a telescoping accident as the user descends from the top of the fly section.
Various devices are known in the prior art for decreasing the possibility of an accidental descent of an extension ladder fly section. In U.S. Pat. No. 201,844 to Smith et al., a hook type rung lock is used to secure ladder sections in an extended position. A spring loaded friction brake is also described, attached to the interior of a rail of the base section. The brake purposely establishes resistance as a fly section is lowered, to slow its descent. The brake is not designed to lock the fly section in place.
West German Patent No. 2610265 describes a spring action locking pin for use with extension ladders. The locking pin is inserted through a hole in the rail of the fly section, from back to front, extending beneath the top rung of the base section. A hook like connector attached to the fly section extends around the top and side of that top rung.
Similarly, West German Patent No. 3611762 describes an attachment to the interior of the rail of a fly section. A hook and latch combination is used to engage the exterior of the top rung of the base section.
Although each of the extension ladder locking devices known in the prior art has particular advantages and purposes, there exists a need for an extension ladder safety device which will serve three purposes:
a. provide a test and indicator of an improper rung lock position, PA1 b. inhibit disturbance of a properly latched fly section, and PA1 c. provide a back-up locking mechanism in addition to properly engaged rung locks.